No abstract

To determine the effects of application rates, grass cover, and formulation type on herbicide losses in runoff, we applied 4.5 kg/ha cyanazine (2‐[(4‐chloro‐6‐(ethylamino)‐1,3,5‐triazin‐2‐yl)] amino]‐2‐methylpropanenitrile) with 0.4 kg/ha sulfometuron‐methyl (methyl‐2[[[[(4,6‐dimethyl‐2‐pyrimidinyl)amino] carbonyl] amino] sulfonyl] benzoate) to 1.2 by 2.4 m plots, using suspension concentrate (SC) and dispersible granule (DG) formulations of cyanazine, and SC and emulsifiable concentrate (EC) formulations of sulfometuron‐methyl. The plots were established on a Tifton loamy sand soil (fine‐loamy, siliceous, thermic Plinthic Paleudults) and had 3% slope. The plots were bare or covered with a mixed stand of common Bermudagrass [Cynodon dactylon (L.) Pers.] and Bahiagrass (Paspalum notatum Flugge var. suarae Parodi). On the day after the herbicides were applied, we simulated rainfall events of 69 mm/h intensity until 2 mm of runoff occurred. The runoff was analyzed for sediment and herbicides. The bare plots required one‐third less rain to produce the same amount of runoff and yielded twice as much sediment as the grassy plots. However, losses of all formulations were 1 to 2% of the amounts applied regardless of grass cover and even though cyanazine rates were 11 times that of sulfometuronmethyl. Total losses of all formulations were sensitive to the length of time between rainfall initiation and runoff initiation, indicating that leaching made herbicide unavailable for runoff. These results suggest that, for these formulations under conditions of similar runoff volumes, losses of pesticides are a fairly constant fraction of the amounts applied, with or without grass cover. For intense storms where the amount of rainfall is similar, chemical runoff from the grassed plots was predicted by computer simulation to be less than half of that from bare soil.

Denitrification is an important potential sink for N in liquid manure and the amount of denitrification may affect sustainability of crops grown with liquid manure as a nutrient source. This study examined gaseous N loss by denitrification and the changes in soil N pools after liquid manure application. Liquid dairy manure was applied at four N rates (246, 427, 643, and 802 kg N ha−1 yr−1) to four quadrants of a center‐pivot in a year‐round forage production system. Denitrification (using the acetylene block technique on intact cores) and soil N pools were determined before and for 2 yr after beginning liquid manure application. Nitrous oxide evolution from soil cores was compared to denitrification for a third year of the study. Denitrification rates and soil N pools increased after manure application at all rates of application. The two highest rates of manure had highest denitrification rates, although differences in soil moisture due to soil and drainage properties complicated the interpretation of manure rate effects. At the two highest rates of N application and two lowest rates of N application, the quadrant with higher soil moisture had higher denitrification. Nitrous oxide emissions accounted for about 29% of total denitrification. Denitrification ranged from 11 to 37% of total N applied in the manure. Highest rates of denitrification and highest proportions of total N denitrified were found with the second highest manure application rate because these soils were wetter. Annual denitrification totals ranged from 32 to 114% of the excess N (application‐crop uptake) available.

R iparian ecosystems are known to be important in the control of nonpoint source pollution and maintenance of healthy aquatic ecosystems (Lowrance et al., 1997). The Riparian Ecosystem Management Model (REMM) (Lowrance et al., In press) has been developed as a tool to aid natural resource agencies and others in making decisions regarding management of riparian buffers to control nonpoint source pollution. REMM is also intended as a tool for researchers to study the complex dynamics of hydrology and water quality functions of riparian ecosystems. The structure of REMM is consistent with buffer system specifications recommended by the U.S. Forest Service and the USDA-Natural Resources Conservation Service as national standards (NRCS, 1995; Welsch, 1991). The specified riparian buffer system consists of three zones parallel to the stream, representing increasing levels of management away from the stream (fig. 1). These zones are zone 1, a narrow, undisturbed native forest area adjacent to the stream for protecting the stream bank and aquatic environment; zone 2, an area with a managed woody vegetation for sequestering sediment and nutrients from upland runoff;

Background: Proven efficacious therapies are sometimes underused in patients with chronic cardiac conditions, resulting in suboptimal outcomes. We evaluated whether evidence summaries, which were either unsigned or signed by local opinion leaders, improved the quality of secondary prevention care delivered by primary care physicians of patients with coronary artery disease. Methods:We performed a randomized trial, clustered at the level of the primary care physician, with 3 study arms: control, unsigned statements or opinion leader statements. The statements were faxed to primary care physicians of adults with coronary artery disease at the time of elective cardiac catheterization. The primary outcome was improvement in statin management (initiation or dose increase) 6 months after catheterization. Results:We enrolled 480 adults from 252 practices. Although statin use was high at baseline (n = 316 [66%]), most patients were taking a low dose (mean 32% of the guideline-recommended dose), and their low-density lipoprotein (LDL) cholesterol levels were elevated (mean 3.09 mmol/L). Six months after catheterization, statin management had improved in 79 of 157 patients (50%) in the control arm, 85 of 158 (54%) patients in the unsigned statement group (adjusted odds ratio [OR] 1.18, 95% CI 0.71-1.94, p = 0.52) and 99 of 165 (60%) patients in the opinion leader statement group (adjusted OR 1.51, 95% CI 0.94-2.42, p = 0.09). The mean fasting LDL cholesterol levels after 6 months were similar in all 3 study arms: 2.35 (standard deviation [SD] 0.86) mmol/L in the control arm compared with 2.24 (SD 0.73) among those in the opinion leader group (p = 0.48) and 2.19 (SD 0.68) in the unsigned statement group (p = 0.32).Interpretation: Faxed evidence reminders for primary care physicians, even when endorsed by local opinion leaders, were insufficient to optimize the quality of care for adults with coronary artery disease. ClinicalTrials.gov trial register no. NCT00175240. AbstractPreviously published at www.cmaj.ca